Prospective Clinical Trial Comparing IV Esmolol to IV Metoprolol in CT Coronary Angiography: Effect on Hemodynamic, Technical Parameters and Cost.

BACKGROUND: Intravenous [IV] esmolol, an alternative to IV metoprolol for coronary computed tomography angiography [CCTA], has shorter half-life that decreases the risk of prolonged hypotension. The primary aim was to prospectively compare IV esmolol alone to IV metoprolol alone for effectiveness in achieving heart rate [HR] of 60 beats per minute[bpm] during CCTA. The secondary aim was to compare hemodynamic response, image quality, radiation dose and cost. MATERIALS AND METHODS: Institutional Review Board approved prospective randomized study of 28 CCTA patients medicated in a 1:1 blinded match with IV esmolol or IV metoprolol to achieve HR of 60 bpm. Serial hemodynamic response was measured at 6 specified times. Two cardiac radiologists independently scored the image quality. RESULTS: Both IV esmolol and IV metoprolol achieved the target HR. IV esmolol resulted in significantly less profound and shorter duration of reduction in systolic blood pressure [BP] than IV metoprolol with a difference of -10, -14 and -9 mm Hg compared to -20, -26 and -25 mmHg at 2, 15 & 30 min respectively. No significant difference in HR at image acquisition, exposure window, radiation dose and image quality. Although IV esmolol was expensive, the overall cost of care was comparable to IV metoprolol due to shortened post CCTA observation period consequent to faster restoration of hemodynamic status. CONCLUSION: Comparison of IV esmolol and IV metoprolol demonstrate that both are effective in achieving the target HR but significantly faster recovery of HR and BP in patients who receive IV esmolol was found.

Patient Preferences for Coronary CT Angiography with Stress Perfusion, SPECT, or Invasive Coronary Angiography.

Background Patient preference is pivotal for widespread adoption of tests in clinical practice. Patient preferences for invasive versus other noninvasive tests for coronary artery disease are not known. Purpose To compare patient acceptance and preferences for noninvasive and invasive cardiac imaging in North and South America, Asia, and Europe. Materials and Methods This was a prospective 16-center trial in 381 study participants undergoing coronary CT angiography with stress perfusion, SPECT, and invasive coronary angiography (ICA). Patient preferences were collected by using a previously validated questionnaire translated into eight languages. Responses were converted to ordinal scales and were modeled with generalized linear mixed models. Results In patients in whom at least one test was associated with pain, CT and SPECT showed reduced median pain levels, reported on 0-100 visual analog scales, from 20 for ICA (interquartile range [IQR], 4-50) to 6 for CT (IQR, 0-27.5) and 5 for SPECT (IQR, 0-25) (P < .001). Patients from Asia reported significantly more pain than patients from other continents for ICA (median, 25; IQR, 10-50; P = .01), CT (median, 10; IQR, 0-30; P = .02), and SPECT (median, 7; IQR, 0-28; P = .03). Satisfaction with preparation differed by continent and test (P = .01), with patients from Asia reporting generally lower ratings. Patients from North America had greater percentages of "very high" or "high" satisfaction than patients from other continents for ICA (96% vs 82%, respectively; P < .001) and SPECT (95% vs 79%, respectively; P = .04) but not for CT (89% vs 86%, respectively; P = .70). Among all patients, CT was preferred by 54% of patients, compared with 18% for SPECT and 28% for ICA (P < .001). Conclusion For cardiac imaging, patients generally favored CT angiography with stress perfusion, while study participants from Asia generally reported lowest satisfaction. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Woodard and Nguyen in this issue.

Renal Hemodynamic Function and RAAS Activation Over the Natural History of Type 1 Diabetes.

RATIONALE & OBJECTIVE: The renin-angiotensin-aldosterone system (RAAS) is associated with renal and cardiovascular disease in diabetes. Unfortunately, early RAAS blockade in patients with type 1 diabetes mellitus (T1DM) does not prevent the development of complications. We sought to examine the role of hyperfiltration and RAAS activation across a wide range of T1DM duration to better understand renal hemodynamic status in patients with T1DM. STUDY DESIGN: Post hoc analysis of blood samples. SETTING & PARTICIPANTS: 148 Canadian patients with T1DM: 28 adolescents (aged 16.2±2.0 years), 54 young adults (25.4±5.6 years), and 66 older adults (65.7±7.5 years) studied in a clinical investigation unit. EXPOSURE: Angiotensin II infusion (1ng/kg/min; a measure of RAAS activation) during a euglycemic clamp. OUTCOMES: Glomerular filtration rate measured using inulin clearance, effective renal plasma flow measured using para-aminohippurate, afferent (RA) and efferent (RE) arteriolar resistances, and glomerular hydrostatic pressure estimated using the Gomez equations. RESULTS: In a stepwise fashion, glomerular filtration rate, effective renal plasma flow, and glomerular hydrostatic pressure were higher, while renal vascular resistance and RA were lower in adolescents versus young adults versus older adults. RE was similar in adolescents versus young adults but was higher in older adults. Angiotensin II resulted in blunted renal hemodynamic responses in older adults (renal vascular resistance increase of 3.3% ± 1.6% vs 4.9% ± 1.9% in adolescents; P<0.001), suggesting a state of enhanced RAAS activation. LIMITATIONS: Homogeneous study participants limit the generalizability of findings to other populations. Studying older adult participants with T1DM may be associated with a survivorship bias. CONCLUSIONS: A state of relatively low RAAS activity and predominant afferent dilation rather than efferent constriction characterize early adolescents and young adults with T1DM. This state of endogenous RAAS inactivity in early T1DM may explain why pharmacologic blockade of this neurohormonal system is often ineffective in reducing kidney disease progression in this setting. Older adults with long-standing T1DM who have predominant afferent constriction and RAAS activation may experience renoprotection from therapies that target the afferent arteriole. Further work is required to understand the potential role of non-RAAS pharmacologic agents that target RA in patients with early and long-standing T1DM.

Association between uric acid, renal haemodynamics and arterial stiffness over the natural history of type 1 diabetes.

AIMS: To examine the relationship between normal plasma uric acid (PUA) levels, renal haemodynamic function, arterial stiffness and plasma renin and aldosterone over a wide range of type 1 diabetes (T1D) durations in adolescents, young adults and older adults. MATERIALS AND METHODS: PUA, glomerular filtration rate (GFR), effective renal plasma flow (ERPF), vascular stiffness parameters (aortic augmentation index [AIx], carotid AIx, carotid femoral pulse wave velocity [cfPWV]), and plasma renin and aldosterone were measured during a euglycaemic clamp in people with T1D: 27 adolescents (mean ± SD age 16.8 ± 1.9 years), 52 young adults (mean ± SD age 25.6 ± 5.5 years) and 66 older adults (mean ± SD age 65.7 ± 7.5 years). RESULTS: PUA was highest in patients with the longest T1D duration: 197 ± 44 µmol/L in adolescents versus 264 ± 82 µmol/L in older adults (P < 0.001). Higher PUA correlated with lower GFR only in older adults, even after correcting for age, glycated haemoglobin and sex (ß = -2.12 ± 0.56; P = 0.0003), but not in adolescents or young adults. Higher PUA correlated with lower carotid AIx (ß = -1.90, P = 0.02) in adolescents. In contrast, PUA correlated with higher cfPWV (P = 0.02) and higher plasma renin (P = 0.01) in older adults with T1D. CONCLUSIONS: The relationship between higher PUA with lower GFR, increased arterial stiffness and renin angiotensin aldosterone system (RAAS) activation was observed only in older adults with longstanding T1D. T1D duration may modify the association between PUA, renal haemodynamic function and RAAS activation, leading to renal vasoconstriction and ischaemia. Further work must determine whether pharmacological PUA-lowering prevents or reverses injurious haemodynamic and neurohormonal sequelae of longstanding T1D, thereby improving clinical outcomes.

The relationships between markers of tubular injury and intrarenal haemodynamic function in adults with and without type 1 diabetes: Results from the Canadian Study of Longevity in Type 1 Diabetes.

OBJECTIVE: Our aim was to define the relationships between plasma biomarkers of kidney injury and intrarenal haemodynamic function (glomerular filtration rate [GFR], effective renal plasma flow [ERPF], renal vascular resistance [RVR]) in adults with type 1 diabetes (T1D). METHODS: The study sample comprised patients with longstanding T1D (duration ≥50 years), among whom 44 were diabetic kidney disease (DKD) resistors (eGFR >60 mL/min/1.73 m2 and <30 mg/d urine albumin excretion) and 22 had DKD, in addition to 73 control participants. GFRINULIN and ERPFPAH were measured, RVR was calculated, and afferent (RA )/efferent (RE ) areteriolar resistances were derived from Gomez equations. Plasma neutrophil gelatinase-associated lipocalin (NGAL), ß2 microglobulin (B2M), osteopontin (OPN) and uromodulin (UMOD) were measured using immunoassay kits from Meso Scale Discovery. RESULTS: Plasma NGAL, B2M and OPN were higher and UMOD was lower in DKD patients vs DKD resistors and non-diabetic controls. In participants with T1D, plasma NGAL inversely correlated with GFR (r = -0.33; P = 0.006) and ERPF (r = -0.34; P = 0.006), and correlated positively with RA (r = 0.26; P = 0.03) and RVR (r = 0.31; P = 0.01). In participants without T1D, NGAL and B2M inversely correlated with GFR (NGAL r = -0.18; P = 0.13 and B2M r = -0.49; P < 0.0001) and with ERPF (NGAL r = -0.19; P = 0.1 and B2M r = -0.42; P = 0.0003), and correlated positively with RA (NGAL r = 0.19; P = 0.10 and B2M r = 0.3; P = 0.01) and with RVR (NGAL r = 0.20; P = 0.09 and B2M r = 0.34; P = 0.003). Differences were significant after adjusting for age, sex, HbA1c, SBP and LDL. There were statistical interactions between T1D status, B2M and intrarenal haemodynamic function (P < 0.05). CONCLUSIONS: Elevated NGAL relates to intrarenal haemodynamic dysfunction in T1D, whereas elevated NGAL and B2M relate to intrarenal haemodynamic dysfunction in adults without T1D. These data may define a diabetes-specific interplay between tubular injury and intrarenal haemodynamic dysfunction.

Risk factors for diabetic kidney disease in adults with longstanding type 1 diabetes: results from the Canadian Study of Longevity in Diabetes.

Objectives: Diabetic kidney disease (DKD) is an independent predictor of cardiovascular morbidity and mortality in type 1 diabetes (T1D). We aimed to explore clinical and biochemical factors, including the achievement of American Diabetes Association (ADA) recommended targets associated with DKD in people living with T1D for ≥50 years. Methods: This was a post hoc analysis of a cross-sectional study of 75 participants enrolled in the Canadian Study of Longevity in T1D. We explored diabetes-related complications, including neuropathy, retinopathy, cardiovascular disease, and DKD. Study participants were dichotomized based on the achievement of ADA recommended targets as the low-target group (achieving ≤4 targets, n = 31) and high-target group (achieving >4 targets, n = 44). The outcome of interest was DKD defined by estimated glomerular filtration rate (eGFR) values <60/mL/min/1.73 m2 and/or 24-h albumin excretion >30 mg. Multivariable logistic regression models were employed to estimate odds ratios (ORs) for DKD with 95% confidence intervals (CIs). Results: Of the 75 participants with prolonged T1D duration (45% male, mean age 66 years), 25 participants had DKD and 50 did not. There was no statistical difference between the high- and low-target groups in terms of age and body mass index. eGFR was significantly higher and the prevalence of diabetic retinopathy was significantly lower in the high-target group. Older age at diagnosis of T1D and lower frequency component to high-frequency component ratio increased the odds of having DKD. Conclusions: In adults with prolonged T1D duration, older age at diagnosis and lower heart rate variability may be associated with DKD.

Quantitative chest CT for subtyping chronic lung allograft dysfunction and its association with survival.

Chronic lung allograft dysfunction (CLAD) is a major cause of mortality in lung transplant recipients. CLAD can be sub-divided into at least 2 subtypes with distinct mortality risk characteristics: restrictive allograft syndrome (RAS), which demonstrates increased overall computed tomography (CT) lung density in contrast with bronchiolitis obliterans syndrome (BOS), which demonstrates reduced overall CT lung density. This study aimed to evaluate a reader-independent quantitative density metric (QDM) derived from CT histograms to associate with CLAD survival. A retrospective study evaluated CT scans corresponding to CLAD onset using pulmonary function tests in 74 patients (23 RAS, 51 BOS). Two different QDM values (QDM1 and QDM2) were calculated using CT lung density histograms. Calculation of QDM1 includes the extreme edges of the histogram. Calculation of QDM2 includes the central region of the histogram. Kaplan-Meier analysis and Cox regression analysis were used for CLAD prognosis. Higher QDM values were significantly associated with decreased survival. The hazard ratio for death was 3.2 times higher at the 75th percentile compared to the 25th percentile using QDM1 in a univariate model. QDM may associate with CLAD patient prognosis.

Optimization of Computed Tomography Coronary Angiography for Improved Plaque Detection.

OBJECTIVE: The study aims to optimize visualization of the coronary wall during computed tomography coronary angiography. METHODS: A coronary plaque phantom was scanned on a wide-volume computed tomography scanner. Spatial resolution, contrast resolution, and vessel wall thickness were measured at different x-ray tube currents and voltages. RESULTS: Spatial resolution ranged from 0.385 to 0.625 mm and was significantly lower at higher currents. Contrast-to-noise ratio was significantly higher at higher currents. The most accurate wall thickness measurements were quantified at 300 and 400 mA for 80 and 100 kVp and 300 mA for 120 and 135 kVp. CONCLUSIONS: Lower spatial resolution at higher currents was due to added blur from increased focal spot size. Contrast-to-noise ratio was higher at higher currents owing to decreased quantum noise. Wall thickness was measured more accurately at intermediate currents with midrange contrast-to-noise ratio but optimal spatial resolution. For accurate coronary wall thickness measurement, contrast-to-noise ratio is compromised to achieve optimal spatial resolution.

Prognostic Value of Combined CT Angiography and Myocardial Perfusion Imaging versus Invasive Coronary Angiography and Nuclear Stress Perfusion Imaging in the Prediction of Major Adverse Cardiovascular Events: The CORE320 Multicenter Study.

Purpose To compare the prognostic importance (time to major adverse cardiovascular event [MACE]) of combined computed tomography (CT) angiography and CT myocardial stress perfusion imaging with that of combined invasive coronary angiography (ICA) and stress single photon emission CT myocardial perfusion imaging. Materials and Methods This study was approved by all institutional review boards, and written informed consent was obtained. Between November 2009 and July 2011, 381 participants clinically referred for ICA and aged 45-85 years were enrolled in the Combined Noninvasive Coronary Angiography and Myocardial Perfusion Imaging Using 320-Detector Row Computed Tomography (CORE320) prospective multicenter diagnostic study. All images were analyzed in blinded independent core laboratories, and a panel of physicians adjudicated all adverse events. MACE was defined as revascularization (>30 days after index ICA), myocardial infarction, or cardiac death; hospitalization for chest pain or congestive heart failure; or arrhythmia. Late MACE was defined similarly, except for patients who underwent revascularization within the first 182 days after ICA, who were excluded. Comparisons of 2-year survival (time to MACE) used standard Kaplan-Meier curves and restricted mean survival times bootstrapped with 2000 replicates. Results An MACE (49 revascularizations, five myocardial infarctions, one cardiac death, nine hospitalizations for chest pain or congestive heart failure, and one arrhythmia) occurred in 51 of 379 patients (13.5%). The 2-year MACE-free rates for combined CT angiography and CT perfusion findings were 94% negative for coronary artery disease (CAD) versus 82% positive for CAD and were similar to combined ICA and single photon emission CT findings (93% negative for CAD vs 77% positive for CAD, P < .001 for both). Event-free rates for CT angiography and CT perfusion versus ICA and single photon emission CT for either positive or negative results were not significantly different for MACE or late MACE (P > .05 for all). The area under the receiver operating characteristic curve (AUC) for combined CT angiography and CT perfusion (AUC = 68; 95% confidence interval [CI]: 62, 75) was similar (P = .36) to that for combined ICA and single photon emission CT (AUC = 71; 95% CI: 65, 79) in the identification of MACE at 2-year follow-up. Conclusion Combined CT angiography and CT perfusion enables similar prediction of 2-year MACE, late MACE, and event-free survival similar to that enabled by ICA and single photon emission CT. © RSNA, 2017 Online supplemental material is available for this article.

The role of biomechanical anatomical modeling via computed tomography for identification of restrictive allograft syndrome.

Chronic lung allograft dysfunction (CLAD) reduces long-term graft survival. It is important to distinguish CLAD subtypes: bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS) as RAS has a worse prognosis and accurate subtyping could facilitate targeted treatments. However, the current diagnosis of CLAD subtypes is based on pulmonary function test (PFT) results that reflect global estimates of lung function; anatomical modeling based on computed tomography (CT) has the potential to provide detailed analysis of global and regional lung function. The purpose of this study is to evaluate the utility of CT-based anatomical modeling for the identification of RAS. This retrospective study included 51 patients (CLAD: 17 BOS and 17 RAS, control: 17 No-CLAD). CT data were assessed using a biomechanical model-based platform (MORFEUS) to characterize changes in lung deformation between baseline and disease onset. Lung deformation demonstrated high sensitivity and specificity (>80%) in differentiating RAS from BOS (P<.0001) and No-CLAD (P<.0001). There were matching radiological reading and inward deformation abnormalities in 79% of lung sections in patients with RAS. Anatomical modeling is complementary to conventional assessment in the diagnosis of RAS and potentially provides quantitative data that can help in the characterization and detailed assessment of heterogeneous lung parenchymal disease.

Cardiovascular disease guideline adherence and self-reported statin use in longstanding type 1 diabetes: results from the Canadian study of longevity in diabetes cohort.

BACKGROUND: Older patients with longstanding type 1 diabetes have high cardiovascular disease (CVD) risk such that statin therapy is recommended independent of prior CVD events. We aimed to determine self-reported CVD prevention guideline adherence in patients with longstanding diabetes. RESEARCH DESIGN AND METHODS: 309 Canadians with over 50 years of type 1 diabetes completed a medical questionnaire for presence of lifestyle and pharmacological interventions, stratified into primary or secondary CVD prevention subgroups based on absence or presence of self-reported CVD events, respectively. Associations with statin use were analyzed using multivariable logistic regression. RESULTS: The 309 participants had mean ± SD age 65.7 ± 8.5 years, median diabetes duration 54.0 [IQR 51.0, 59.0] years, and HbA1c of 7.5 ± 1.1 % (58 mmol/mol). 159 (52.7 %) participants reported diet adherence, 296 (95.8 %) smoking avoidance, 217 (70.5 %) physical activity, 218 (71.5 %) renin-angiotensin-system inhibitor use, and 220 (72.1 %) statin use. Physical activity was reported as less common in the secondary prevention subgroup, and current statin use was significantly lower in the primary prevention subgroup (65.5 % vs. 84.8 %, p = 0.0004). In multivariable logistic regression, the odds of statin use was 0.38 [95 % CI 0.15-0.95] in members of the primary compared to the secondary prevention subgroup, adjusting for age, sex, hypertension history, body mass, HbA1c, cholesterol, microvascular complications, acetylsalicylic acid use, and renin-angiotensin system inhibitor use. CONCLUSION: Despite good self-reported adherence to general CVD prevention guidelines, against the principles of these guidelines we found that statin use was substantially lower in those without CVD history. Interventions are needed to improve statin use in older type 1 diabetes patients without a history of CVD.

Randomized controlled trial of relaxation music to reduce heart rate in patients undergoing cardiac CT.

OBJECTIVES: To evaluate the heart rate lowering effect of relaxation music in patients undergoing coronary CT angiography (CCTA), pulmonary vein CT (PVCT) and coronary calcium score CT (CCS). METHODS: Patients were randomised to a control group (i.e. standard of care protocol) or to a relaxation music group (ie. standard of care protocol with music). The groups were compared for heart rate, radiation dose, image quality and dose of IV metoprolol. Both groups completed State-Trait Anxiety Inventory anxiety questionnaires to assess patient experience. RESULTS: One hundred and ninety-seven patients were recruited (61.9 % males); mean age 56y (19-86 y); 127 CCTA, 17 PVCT, 53 CCS. No significant difference in heart rate, radiation dose, image quality, metoprolol dose and anxiety scores. 86 % of patients enjoyed the music. 90 % of patients in the music group expressed a strong preference to have music for future examinations. The patient cohort demonstrated low anxiety levels prior to CT. CONCLUSION: Relaxation music in CCTA, PVCT and CCS does not reduce heart rate or IV metoprolol use. Patients showed low levels of anxiety indicating that anxiolytics may not have a significant role in lowering heart rate. Music can be used in cardiac CT to improve patient experience. KEY POINTS: • Relaxation music does not reduce heart rate in cardiac CT • Relaxation music does not reduce beta-blocker use in cardiac CT • Relaxation music has no effect on cardiac CT image quality • Low levels of anxiety are present in patients prior to cardiac CT • Patients enjoyed the relaxation music and this results in improved patient experience.

State of the Art: Iterative CT Reconstruction Techniques.

Owing to recent advances in computing power, iterative reconstruction (IR) algorithms have become a clinically viable option in computed tomographic (CT) imaging. Substantial evidence is accumulating about the advantages of IR algorithms over established analytical methods, such as filtered back projection. IR improves image quality through cyclic image processing. Although all available solutions share the common mechanism of artifact reduction and/or potential for radiation dose savings, chiefly due to image noise suppression, the magnitude of these effects depends on the specific IR algorithm. In the first section of this contribution, the technical bases of IR are briefly reviewed and the currently available algorithms released by the major CT manufacturers are described. In the second part, the current status of their clinical implementation is surveyed. Regardless of the applied IR algorithm, the available evidence attests to the substantial potential of IR algorithms for overcoming traditional limitations in CT imaging.

Comprehensive assessment of radiation dose estimates for the CORE320 study.

OBJECTIVE. The purpose of this study was to comprehensively study estimated radiation doses for subjects included in the main analysis of the Combined Non-invasive Coronary Angiography and Myocardial Perfusion Imaging Using 320 Detector Computed Tomography (CORE320) study ( ClinicalTrials.gov identifier NCT00934037), a clinical trial comparing combined CT angiography (CTA) and perfusion CT with the reference standard catheter angiography plus myocardial perfusion SPECT. SUBJECTS AND METHODS. Prospectively acquired data on 381 CORE320 subjects were analyzed in four groups of testing related to radiation exposure. Radiation dose estimates were compared between modalities for combined CTA and perfusion CT with respect to covariates known to influence radiation exposure and for the main clinical outcomes defined by the trial. The final analysis assessed variations in radiation dose with respect to several factors inherent to the trial. RESULTS. The mean radiation dose estimate for the combined CTA and perfusion CT protocol (8.63 mSv) was significantly (p < 0.0001 for both) less than the average dose delivered from SPECT (10.48 mSv) and the average dose from diagnostic catheter angiography (11.63 mSv). There was no significant difference in estimated CTA-perfusion CT radiation dose for subjects who had false-positive or false-negative results in the CORE320 main analyses in a comparison with subjects for whom the CTA-perfusion CT findings were in accordance with the reference standard SPECT plus catheter angiographic findings. CONCLUSION. Radiation dose estimates from CORE320 support clinical implementation of a combined CT protocol for assessing coronary anatomy and myocardial perfusion.

Computed tomography angiography and perfusion to assess coronary artery stenosis causing perfusion defects by single photon emission computed tomography: the CORE320 study.

AIMS: To evaluate the diagnostic power of integrating the results of computed tomography angiography (CTA) and CT myocardial perfusion (CTP) to identify coronary artery disease (CAD) defined as a flow limiting coronary artery stenosis causing a perfusion defect by single photon emission computed tomography (SPECT). METHODS AND RESULTS: We conducted a multicentre study to evaluate the accuracy of integrated CTA-CTP for the identification of patients with flow-limiting CAD defined by ≥50% stenosis by invasive coronary angiography (ICA) with a corresponding perfusion deficit on stress single photon emission computed tomography (SPECT/MPI). Sixteen centres enroled 381 patients who underwent combined CTA-CTP and SPECT/MPI prior to conventional coronary angiography. All four image modalities were analysed in blinded independent core laboratories. The prevalence of obstructive CAD defined by combined ICA-SPECT/MPI and ICA alone was 38 and 59%, respectively. The patient-based diagnostic accuracy defined by the area under the receiver operating characteristic curve (AUC) of integrated CTA-CTP for detecting or excluding flow-limiting CAD was 0.87 [95% confidence interval (CI): 0.84-0.91]. In patients without prior myocardial infarction, the AUC was 0.90 (95% CI: 0.87-0.94) and in patients without prior CAD the AUC for combined CTA-CTP was 0.93 (95% CI: 0.89-0.97). For the combination of a CTA stenosis ≥50% stenosis and a CTP perfusion deficit, the sensitivity, specificity, positive predictive, and negative predicative values (95% CI) were 80% (72-86), 74% (68-80), 65% (58-72), and 86% (80-90), respectively. For flow-limiting disease defined by ICA-SPECT/MPI, the accuracy of CTA was significantly increased by the addition of CTP at both the patient and vessel levels. CONCLUSIONS: The combination of CTA and perfusion correctly identifies patients with flow limiting CAD defined as ≥50 stenosis by ICA causing a perfusion defect by SPECT/MPI.

Use of Cardiac Magnetic Resonance Imaging Based Measurements of Inferior Vena Cava Cross-Sectional Area in the Diagnosis of Pericardial Constriction.

PURPOSE: To evaluate the value of cardiac magnetic resonance imaging (MRI)-based measurements of inferior vena cava (IVC) cross-sectional area in the diagnosis of pericardial constriction. METHODS: Patients who had undergone cardiac MRI for evaluation of clinically suspected pericardial constriction were identified retrospectively. The diagnosis of pericardial constriction was established by clinical history, echocardiography, cardiac catheterization, intraoperative findings, and/or histopathology. Cross-sectional areas of the suprahepatic IVC and descending aorta were measured on a single axial steady-state free-precession (SSFP) image at the level of the esophageal hiatus in end-systole. Logistic regression and receiver-operating curve (ROC) analyses were performed. RESULTS: Thirty-six patients were included; 50% (n = 18) had pericardial constriction. Mean age was 53.9 ± 15.3 years, and 72% (n = 26) were male. IVC area, ratio of IVC to aortic area, pericardial thickness, and presence of respirophasic septal shift were all significantly different between patients with constriction and those without (P < .001 for all). IVC to aortic area ratio had the highest odds ratio for the prediction of constriction (1070, 95% confidence interval [8.0-143051], P = .005). ROC analysis illustrated that IVC to aortic area ratio discriminated between those with and without constriction with an area under the curve of 0.96 (95% confidence interval [0.91-1.00]). CONCLUSIONS: In patients referred for cardiac MRI assessment of suspected pericardial constriction, measurement of suprahepatic IVC cross-sectional area may be useful in confirming the diagnosis of constriction when used in combination with other imaging findings, including pericardial thickness and respirophasic septal shift.

How influential is the duration of contrast material bolus injection in perfusion CT? evaluation in a swine model.

PURPOSE: To analyze the effect of the duration of contrast material bolus injection on perfusion values in a swine model by using the maximum slope method. MATERIALS AND METHODS: This study was approved by the institutional animal care committee. Twenty pigs (weight range, 63-77 kg) underwent dynamic volume computed tomography (CT) of the kidneys during suspended respiration. Before the CT examination, a miniature cuff-shaped ultrasonographic flow probe encircling the right renal artery was surgically implanted in each pig to obtain true perfusion values. Two sequential perfusion CT series were performed in 30 seconds, each comprising 30 volumes with identical parameters (100 kV, 200 mAs, 0.5 sec rotation time). The duration of contrast material bolus (0.5 mL/kg of body weight) was 3.8 seconds in the first series (short bolus series) and 11.5 seconds in the second series (long bolus series), and the injection flow rate was adapted accordingly. In each pig, cortical kidney volume was determined by using the volume with the highest cortical enhancement. CT perfusion values were calculated for both series by using the maximum slope method and were statistically compared and correlated with the true perfusion values from the flow probe by using linear regression analysis. RESULTS: Mean true perfusion and CT perfusion values (in minutes(-1)) for the short bolus series were 1.95 and 2.03, respectively (P = .22), and for the long bolus series, they were 2.02 and 1.92, respectively (P = .12). CT perfusion showed very good correlation with true perfusion in both the short (slope, 1.01; 95% confidence interval: 0.91, 1.11) and long (slope, 0.92; 95% confidence interval: 0.78, 1.04) series. On the basis of the regression analysis, CT perfusion values in the short bolus series were overestimated by 1% and those in the long bolus series were underestimated by 8%. CONCLUSION: Duration of contrast material bolus injection does not influence CT perfusion values substantially. The longer, clinically preferred intravenous injection scheme is sufficiently accurate for CT perfusion.

Optimal image reconstruction for detection and characterization of small pulmonary nodules during low-dose CT.

OBJECTIVES: To optimize the slice thickness/overlap parameters for image reconstruction and to study the effect of iterative reconstruction (IR) on detectability and characterization of small non-calcified pulmonary nodules during low-dose thoracic CT. MATERIALS AND METHODS: Data was obtained from computer simulations, phantom, and patient CTs. Simulations and phantom CTs were performed with 9 nodules (5, 8, and 10 mm with 100, -630, and -800 HU). Patient data were based on 11 ground glass opacities (GGO) and 9 solid nodules. For each analysis the nodules were reconstructed with filtered back projection and IR algorithms using 10 different combinations of slice thickness/overlap (0.5-5 mm). The attenuation (CT#) and the contrast to noise ratio (CNR) were measured. Spearman's coefficient was used to correlate the error in CT# measurements and slice thickness. Paired Student's t test was used to measure the significance of the errors. RESULTS: CNR measurements: CNR increases with increasing slice thickness/overlap for large nodules and peaks at 4.0/2.0 mm for smaller ones. Use of IR increases the CNR of GGOs by 60 %. CT# measurements: Increasing slice thickness/overlap above 3.0/1.5 mm results in decreased CT# measurement accuracy. CONCLUSION: Optimal detection of small pulmonary nodules requires slice thickness/overlap of 4.0/2.0 mm. Slice thickness/overlap of 2.0/2.0 mm is required for optimal nodule characterization. IR improves conspicuity of small ground glass nodules through a significant increase in nodule CNR. KEY POINTS: • Slice thickness/overlap affects the accuracy of pulmonary nodule detection and characterization. • Slice thickness ≥3 mm increases the risk of misclassifying small nodules. • Optimal nodule detection during low-dose CT requires 4.0/2.0-mm reconstructions. • Optimal nodule characterization during low-dose CT requires 2.0/2.0-mm reconstructions. • Iterative reconstruction improves the CNR of ground glass nodules by 60 %.

Image noise-based dose adaptation in dynamic volume CT of the heart: dose and image quality optimisation in comparison with BMI-based dose adaptation.

OBJECTIVES: To compare the image quality and radiation dose using image-noise (IN)-based determination of X-ray tube settings compared with a body mass index (BMI)-based protocol during CT coronary angiography (CTCA). METHODS: Two hundred consecutive patients referred for CTCA to our institution were divided into two groups: BMI-based, 100 patients had CTCA with the X-ray tube current adjusted to the patient's BMI while maintaining a fixed tube potential of 120 kV; IN-based, 100 patients underwent imaging with the X-ray tube current and voltage adjusted to the IN measured within the mid-left ventricle on a pre-acquisition trans-axial image. Two independent cardiac radiologists performed blinded image quality assessment with quantification of the IN and signal-to-noise ratio (SNR) from the mid-LV and qualitative assessment using a three-point score. Radiation dose (CTDI and DLP) was recorded from the console. RESULTS: Results showed: IN (HU): BMI-based, 30.1 ± 9.9; IN-based, 33.1 ± 6.7; 32 % variation reduction (P = 0.001); SNR: BMI-based, 18.6 ± 7.1; IN-based, 15.4 ± 3.7; 48 % variation reduction (P < 0.0001). Visual scores: BMI-based, 2.3 ± 0.6; IN-based, 2.2 ± 0.5 (P = 0.54). Radiation dose: CTDI (mGy), BMI-based, 22.68 ± 8.9; IN-based, 17.16 ± 7.6; 24.3 % reduction (P < 0.001); DLP (mGy.cm), BMI-based, 309.3 ± 127.5; IN-based, 230.6 ± 105.5; 25.4 % reduction (P < 0.001). CONCLUSIONS: Image-noise-based stratification of X-ray tube parameters for CTCA results in 32 % improvement in image quality and 25 % reduction in radiation dose compared with a BMI-based protocol. KEY POINTS: • Image quality and radiation dose are closely related in CT coronary angiography. • So too are the image quality, radiation dose and body mass index (BMI). • An image-noise-based CTCA protocol reduces the radiation dose by 25 %. • It improves inter-patient image homogeneity by 32 %.

Diagnostic Accuracy in Detecting Fungal Infection with Ultra-Low-Dose Computed Tomography (ULD-CT) Using Filtered Back Projection (FBP) Technique in Immunocompromised Patients.

Purpose: To compare the accuracy of ultra-low-dose (uLDCT) to standard-of-care low-dose chest CT (LDCT) in the detection of fungal infection in immunocompromised (IC) patients. Method and Materials: One hundred IC patients had paired chest CT scans performed with LDCT followed by uLDCT. The images were independently reviewed by three chest radiologists who assessed the image quality (IQ), diagnostic confidence, and detection of major (macro nodules, halo sign, cavitation, consolidation) and minor (4-10 mm nodules, ground-glass opacity) criteria for fungal disease using a five-point Likert score. Discrepant findings were adjudicated by a fourth chest radiologist. Box-whisker plots were used to analyze IQ and diagnostic confidence. Inter-rater reliability was assessed using interclass correlation coefficients (ICCs). The statistical difference between LDCT and uLDCT results was assessed using Wilcoxon paired test. Results: Lung reconstructions had IQ and diagnostic confidence scores (mean ± std) of 4.52 ± 0.47 and 4.63 ± 0.51 for LDCT and 3.85 ± 0.77 and 4.01 ± 0.88 for uLDCT. The images were clinically acceptable except for uLDCT in obese patients (BMI ≥ 30 kg/m2), which had an IQ ranking from poor to excellent (scores 1 to 5). The accuracy in detecting major and minor radiological findings with uLDCT was 96% and 84% for all the patients. The inter-rater agreements were either moderate, good, or excellent, with ICC values of 0.51-0.96. There was no significant statistical difference between the uLDCT and LDCT ICC values (p = 0.25). The effective dose for uLDCT was one quarter that of LDCT (CTDIvol = 0.9 mGy vs. 3.7 mGy). Conclusions: Thoracic uLDCT, at a 75% dose reduction, can replace LDCT for the detection of fungal disease in IC patients with BMI < 30.0 kg/m2.